1. Field of the Invention
The present invention relates to ignition coils and cores for the same along with a method of making the same and, more specifically, it relates to an improved construction of such cores.
2. Description of the Prior Art
In connection with ignition coils, such as those used in internal combustion engines, it has been known to provide a transformer having a magnetic core with a surrounding primary coil which is adapted to be energized in order to generate a magnetic field, along with a secondary coil which, as a result of such magnetic field, receives an induced electromotive force.
As the result of the difficulty in machining silicon steel, it has been suggested previously to assemble a plurality of laminated plates to create a stepped profile for the core. See U.S. Pat. Nos. 5,986,532 and 6,025,770.
It has also been suggested to provide an epoxy material over the outer stepped configuration. See U.S. Pat. No. 4,663,604.
It has been known in recent years to provide auto ignitions which rather than having a single ignition coil providing energy to each spark plug has a single smaller coil for each spark plug in the internal combustion engine. As the length of such a laminated stack core may be on the order of ten times the widest lamination, these cores are frequently designated as xe2x80x9cpencil cores.xe2x80x9d
With the prior art laminated externally stepped construction, the cross-section was generally round, but as a result of the steps and the flattened top and bottom laminations, the construction did not approximate a circular profile. This served to reduce the weight of the stepped core per unit length, as a result of the reduced total amount of metal as compared with a circular shape. Further, in view of the sharp edges on the individual lamina, an insulator had to be added thereover in order to resist cutting the wire wrapped around the laminations.
There remains, therefore, a need for an improved construction for ignition cores.
The present invention has met the above-described need by providing an ignition coil and core as well as the method of making the same, which eliminates the prior art problems hereinbefore described.
As employed herein, the term xe2x80x9cautomotive ignitionxe2x80x9d means ignitions for internal combustion engines for vehicles, including, but not limited to, automobiles, sports utility vehicles, trucks, boats, airplanes, locomotives, and other land vehicles powered by internal combustion engines, as well as other equipment employing spark plugs.
As employed herein, the term xe2x80x9csubstantially circularxe2x80x9d means either (a) circular, or (b) a configuration which apart from a single pair of opposed flat plate portions at the upper and lower extremities (if present) is substantially circular and expressly excludes previously known conventional stepped circumferential configurations.
The present invention provides an ignition coil, which may be an automotive ignition coil, which has an elongated substantially circular coil core and a radially outwardly disposed primary coil and a radially outwardly disposed secondary coil. The core is composed of a plurality of generally rectangular elements, at least some of which have different widths than others with the adjacent elements being in surface-to-surface contact with each other.
The sidewalls of the individual elements may be curved or have other configurations which are not generally perpendicular to the longitudinal extent of the elements. The assembly of elements is joined to each other preferably by welding at the ends.
In the preferred method of manufacturing the ignition coil core, a plurality of generally rectangular elongated generally flat elements, at least some of which have different widths, are assembled with the elements of greatest width positioned in the center and elements of progressively reduced width being provided on opposed sides thereof. While the starting point could be elements of the same width, this would be wasteful of material. The individual elements are then subjected to machining of the lateral edges to establish the configuration of a substantially circular core cross-sectional shape. The machining preferably involves mechanical machining followed by electrochemical machining. Subsequently, the assembly of reformed core elements is joined as by welding or other suitable means which will be known to those skilled in the art. In a preferred practice, deburring is provided.
It is an object of the present invention to provide an improved ignition coil having a uniquely configurated core configuration and a method of manufacturing the same.
It is a further object of the present invention to provide such an ignition coil which is adapted to be employed with conventional coil construction and energizing means.
It is a further object of the present invention to provide such a core that has a smooth outer surface which eliminates the need to coat the exterior surface thereof.
It is a further object of the present invention to provide such cores which are of uniform quality and performance characteristics from core to core.
It is a further object of the present invention to provide such cores which as a result of the substantially circular configuration has increased weight for a given diameter as compared with a corresponding stepped core of the same diameter or maximum transverse direction.
It""s another object of the present invention to provide a core having improved electrical performance characteristics.
It is a farther object of the present invention to provide a method for making a substantially circular ignition coil and the resulting core.
It is a further object of the present invention to provide such an ignition core, which eliminates the need for providing an insulator therearound to resist cutting the wire laminations wrapped around the core.
It is a further object of the present invention to provide such an ignition core which can be manufactured economically and rapidly.
These and other objects of the present invention will be more fully understood from the following detailed description of the invention on reference to the illustrations appended hereto.